''Fukuipteryx'' is an extinct genus of basal

avialan Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally used ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s found in

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

deposits from

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

Kitadani Formation The Kitadani Formation ( ja, 北谷層 ''Kitadani-sō'') is a unit of Lower Cretaceous sedimentary rock which crops out near the city of Katsuyama in Fukui Prefecture, Japan, and it is the primary source of Cretaceous-aged non-marine vertebrate f ...

. It contains one species, ''Fukuipteryx prima''.Imai, T., Azuma, Y., Kawabe, S., Shibata, M., Miyata, K., Wang, M., & Zhou, Z. (2019)
An unusual bird (Theropoda, Avialae) from the Early Cretaceous of Japan suggests complex evolutionary history of basal birds
Communications Biology, 2(1). doi: 10.1038/s42003-019-0639-4

Discovery and naming

In 2013, the first associated skeleton of an Early Cretaceous avialan from Japan was collected at the Kitadani Dinosaur Quarry in Katsuyama,

Fukui is a Japanese name meaning "fortunate" or sometimes "one who is from the Fukui prefecture". It may refer to: Places * Fukui Domain, a part of the Japanese han system during the Edo period * Fukui Prefecture, a prefecture of Japan located in ...

, central Japan. The specimen is three-dimensionally preserved, and exhibits several autapomorphies, which led to the creation of a new taxon. In 2019, the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

''Fukuipteryx prima'' was named and described by Takuya Imai, Yoichi Azuma, Soichiro Kawabe, Masateru Shibata, Kazunori Miyata, Wang Min and Zhou Zhonghe. The genus name combines a reference to Fukui with the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

''pteryx'', meaning "feather". The specific name means "the first" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

and refers to its basal position on the avialan phylogenetic tree. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, FPDM-V-9769, was found in a layer of green sandstone from the Kitadani Formation that dates from the

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

, about 120 million years old. It consists of a partial skeleton with a lower jaw. In total, a right surangular, two cervical vertebrae, four back vertebrae, two sacral vertebrae, five tail vertebrae, the pygostyle, ribs, a wishbone, both coracoid pelvis bones, the right ilium bone, the left upper arm bone, the ulna and radius of both forearms, the second right metacarpal, the left hand and both lower hindlimbs minus the calf bones and toes are preserved. The skeleton is not articulated but is preserved three-dimensionally. It is a subadult animal, less than one year old. It is part of the collection of the

Fukui Prefectural Dinosaur Museum The , located in Katsuyama, Fukui, Japan, is one of the leading dinosaur museums in Asia that is renowned for its exhibits of fossil specimens of dinosaurs and paleontological research. It is sited in the Nagaoyama Park ( Katsuyama Dinosaur For ...

. The fossil was not fully prepared from its matrix and the bones were reconstructed via a CAT-scan.

Description

''Fukuipteryx'' was about the size of a modern

pigeon Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...

. ''Fukuipteryx'' shows several

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

(unique derived characters) that indicate that it was not a very basal species, in the sense that it would be outside of Avialae. A

pygostyle Pygostyle describes a skeletal condition in which the final few caudal vertebrae are fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these. The pygostyle is the main compon ...

, a fusion of the posterior tail vertebrae, is present, suggesting that the loss of a long tail was a less important step in the evolution of flight than was previously thought. The pygostyle is robust with rudiments of

neural spine The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

s still visible, while the rear end has a paddle-shaped structure. The

furcula The (Latin for "little fork") or wishbone is a forked bone found in most birds and some species of non-avian dinosaurs, and is formed by the fusion of the two pink clavicles. In birds, its primary function is in the strengthening of the thoracic ...

is robust and U-shaped, but the angle between the branches is not very large. The

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

is a long strut, not fused to the shoulder blade. The

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

is the largest bone of the limbs. The humerus has a round depression on the front top of its head. The shaft of the humerus is bent upwards (with the wing in a horizontal position). The

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

and

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

are longer than the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

Phylogeny

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis recovered ''Fukuipteryx'' as an early-diverging avialan closer to modern birds than to ''

Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

'', but more basal than ''

Jeholornis ''Jeholornis'' (meaning "Jehol bird") is a genus of avialans that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China. Fossil ''Jeholornis'' were first discovered in the Jiufotang Formation in Heb ...

''. Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

following that analysis:

References

{{Taxonbar, from=Q75218540 Prehistoric avialans Aptian genera Early Cretaceous dinosaurs of Asia Cretaceous Japan Fossils of Japan Fossil taxa described in 2019 Taxa named by Zhou Zhonghe